How do you carry out Tollens' reagent test?
1 Answer
Here's how you do it…
Prepare the reagent
Prepare the reagent by adding
Do the test
To carry out the test, add a few drops of the unknown to the freshly prepared reagent in a clean test tube, and warm gently for a few minutes in a hot water bath.
The formation of a grey-black precipitate or a silver mirror on the inside of the test tube is a positive result.
Why it works
The Tollens reagent is a colourless solution of
1.
#"2AgNO"_3 + "2NaOH" → "Ag"_2"O" + "2NaNO"_3 + "H"_2"O"#
2. Aqueous
#"Ag"_2"O"+ "4NH"_3 + "H"_2"O" → "2Ag"("NH"_3)_2^+ + "2OH"^"-"#
3. The
If you are lucky, a silver mirror forms on the inside of the test tube; if you are unlucky, you get a grey-black precipitate of silver.
The Tollens reagent does not oxidize ketones, so the Tollens test distinguishes aldehydes from ketones.